PSI - Issue 2_B

Beatriz Sanz et al. / Procedia Structural Integrity 2 (2016) 2849–2856 B. Sanz et al. / Structural Integrity Procedia 00 (2016) 000–000

2855

7

0.0958 w (mm)

sigm

0.0958 w (mm)

sigma_I (MPa)

0

0.192

0

1.39

2.78

0

0.192

0

0.0958 w (mm)

sigma_I (MPa)

0

0.192

0

1.39

2.78

(a) (c) Fig. 6. Results of simulations of accelerated corrosion tests and experimental results: curves of variation of capillary height (a) and of variation of inner diameter (b), and simulated stress map and crack pattern for a corrosion depth of 20 µ m (c). See Fig. 6(d) for the results of main CMOD. (b)

From the foregoing results, it is concluded that the main CMOD of prisms with a tube is more sensitive to variations in the oxide parameters than that of prisms with a bar. Besides, prisms with a tube provided extra information about the variation of inner volume –measured through the capillary height– and inner diameter of the tube, which result to be much more sensitive to variations in the oxide parameters than the main CMOD. As an example, Figs. 5(d) and (e) display the e ff ect of the shear sti ff ness k 0 t on the curves of capillary height and inner diameter. Then the best values for the model parameters were determined, taking as a reference the experimental results obtained in Sanz et al. (2015). Firstly the expansion factor β , which scales the curves of results on the corrosion-depth axis as shown in Fig. 5(f), was modified until the numerical curves fitted the experimental ones, finding that the best value was β = 2 . 0. Next, the shear sti ff ness k 0 t was adjusted, using the new value of β and bilinear softening with fracture energy G F = 0 . 107 N / mm and stress at the kink point σ k = 0 . 322MPa, finding that k 0 t = 1000N / mm 3 was the best value for that. Figs. 6(a) and (b) display the resulting curves of variation of capillary height and inner diameter, showing a good agreement with the experimental results. Finally, it was assessed that the crack pattern at the end of the simulations, Fig. 6(c), resembled the experimental one, which consisted of a main crack and between four and eight secondary cracks surrounding the reinforcement, as observed in slices of the specimens impregnated with fluorescent resin (Sanz et al., 2013). For completeness of this study, the e ff ect of the fracture energy of the linear curve G F 1 is shown in Fig. 7. As observed for the oxide parameters, the e ff ect was greater on the curves of variation of capillary height, Fig. 7(a), and inner diameter than on the curves of main CMOD Fig. 7(b). A numerical study has been carried out to investigate the influence of the oxide parameters on the results of ac celerated corrosion of reinforced concrete structures. For that, two-dimensional models of concrete prisms reinforced with a bar and prisms reinforced with a tube have been used. A model has been applied that reproduces the cohesive fracture of concrete and the expansive behavior of the oxide. The results have been compared with those of accelerated corrosion tests designed with conditions reproduceable in two-dimensional models. From the study, it has been observed that the measurement of main CMOD is more a ff ected by variations in the oxide parameters in models with a tube than in models with a bar. Besides, the curves of variation of inner diameter and capillary height recorded in prisms with a tube are much more sensitive than the main CMOD to the oxide and concrete parameters. Thus, using prisms reinforced with a tube has been crucial in this research to obtain the best values for the constitutive parameters of the oxide, which could be applied in further studies. 4. Conclusions